The present invention is directed to an explosive charge operated device for driving fastening elements and includes an axially displaceable barrel with a driving piston guided in the barrel. Flow passageways are provided from the barrel for discharging propellant gases out of the barrel into the atmosphere.
Soundproofing is a considerable problem in explosive powder operated devices for driving fastening elements. A very high sound level is generated by the propellant gases flowing out of the device at a high velocity. The high sound level has an annoying effect in the region where the device is used and in particular on the device operator. Devices are known for driving fastening elements using an integrated or attached silencer. Such silencers are based on the expansion principle where the gases generated in the firing of the explosive charge are discharged from the device through one or a number of expansion chambers into the atmosphere. Openings are located between the expansion chambers with a more or less large cross-section. In the region of the openings the propellant gases flow at a relatively high velocity and in the subsequent expansion chambers a reduction in the velocity energy takes place due to the turbulence of the gases.
Up until the present time, the silencers used have resulted in a relatively high loss of the fastening element driving energy. In particular, if the exhaust openings are exposed relatively early in the displacement of the driving piston in the driving direction, a large portion of the propellant gases escape practically unused into the atmosphere. Moreover, if the exhaust openings are opened in a latter phase of the driving operation, a very rapid rise takes place in the sound level attaining a high peak value.